1. Field of the Invention
The present invention relates generally to medical methods and devices. More particularly, the present invention relates to methods and systems for expanding tissue by delivering incremental volumes of an inflation medium to an implanted expandable bladder while monitoring inflation pressure.
Tissue defects in the skin and other tissues occur from a variety of causes including surgery, burns, traumatic injury, and congenital deformities. Such defects are often characterized by tissue “deficits” where there is insufficient or poor quality skin or tissue present to cover or fill the affected body region in a normal or desired profile or pattern.
Tissue deficit may be treated by stimulating skin expansion and/or tissue growth in the region of the defect. For example, “tissue expanders” may be implanted beneath a region of skin or within a volume of tissue which suffer from the deficit. By gradually inflating or otherwise expanding such tissue expander, the growth of skin and/or tissue can be promoted.
Presently, most tissue expanders are in the form of an implantable balloon with a valve that allows a physician to periodically inflate the balloon to increase its volume over successive office visits. As the patient will typically visit the doctor only about once per week, such periodic inflations often require relatively large volumes of inflation medium which can cause not only patient discomfort, but also tissue ischemia, concavities to underlying structures such as bone, and induce encapsulation of the implant causing capsular contracture and stiffening of tissue around the expander.
In order to address such shortcomings, a number of “continuously” expanding devices have been proposed. For example, in U.S. Patent Publication 2010/0010531, a device is described which allows the patient to periodically trigger a gas source within the implanted expander. Allowing the patient to control expansion, however, has its own drawbacks, and the patient will seldom follow an optimum inflation protocol to achieve the desired tissue expansion. Moreover, the use of a gas as the inflation medium is also disadvantageous.
A particular improvement in this field is found in U.S. Patent Publication No. 2013/0079807, commonly assigned with the present application, which describes a tissue expansion system including a pump, a controller, an inflatable bladder, and a pressure sensor. The pump is adapted for substantially continuous operation in response to a pressure within a subcutaneously inflatable bladder during expansion. Delivery is based solely on monitored pressure, which can sometimes result in overly rapid treatment.
For these reasons, it would be desirable to provide improved and alternative tissue expansion devices. In particular, it would be desirable to provide such devices which continuously and automatically deliver an inflation medium to an implanted expander over time in a more optimal and controlled pattern. It would be further desirable if such expanders and their supporting systems were adapted for patient convenience and comfort to further promote their use. It would be further desirable if such expanders were operated based on parameters in addition to pressure and the other parameters described above. At least some of these objectives will be met by the inventions described here and below.
2. Description of the Background Art
U.S. Patent Publication No. 2013/0079807, commonly assigned with the present application, describes a tissue expansion system including a pump, a controller, and inflatable bladder, and a pressure sensor. The pump is adapted for substantially continuous operation in response to a pressure within a subcutaneously the inflatable bladder during expansion. Other relevant patents and publications include U.S. Pat. Nos. 6,668,836; 6,432,081; 5,549,672; 5,496,368; 5,005,591; 5,092,348; 4,955,905; and U.S. Patent Publications 2011/152913; 2010/010531; 2008/051822; and 2004/147953. See also Logan and Hayden (1989) ISA, Paper #89-0207, pp. 27-33.